White balance control device employing zoom information for photographing an object without the occurrence of color failure

ABSTRACT

A white balance control device is provided for use in a video camera or a still video camera, each having zoom capabilities, in which white balance control signals are controlled so that an object may be photographed without the occurrence of color failure. A recognition level or threshold is set as a function of zoom information. A microcomputer of the white balance control device detects a difference between integral averaged values for two color difference signals R-Y and B-Y and a reference value. Depending on the difference, values of the white balance control signals Rcont and Bcont may be changed when the brightness of an object is changed by more than the recognition level. However, the values are positioned within a variable region and when the values of the white balance control signals Rcont and Bcont become constant, the variable region is renewed.

This application is a divisional of application Ser. No. 07/932,488,filed on Jul. 31, 1992, now U.S. Pat. No. 5,329,361 the entire contentsof which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a white balance control device of avideo camera and a video still camera, and particularly to a whitebalance control device for properly controlling white balance by amethod of inside light measurement without color failure occurring, awhite balance control device for accurately controlling white balance byreducing the white balance converging period, a white balance controldevice for properly controlling white balance control by a method ofinside light measurement without color failure occurring whenphotographing indoors and outdoors, a white balance control device witha device for selecting a light source by manual operation in order toprevent deterioration of reproduced colors caused by a differencebetween a data of a selected light source and an acutal colortemperature of the selected light source.

2. Related Art

In conventional video cameras and video still cameras, a white balancecontrol is utilized in order to reproduce a white object as a whitecolored material. The white balance control is operated by controlling again of a red signal circuit and a gain of a blue signal circuit in thecamera based on a Green signal as a reference value.

In the white balance control, it is necessary to measure a tint (colortemperature) of a photographing working field for operating the whitebalance control. As methods of the white balance control, there are anoutside light measuring method and an inside light measuring method,which are different from each other in measuring the color temperatureof the photographing working field.

In the outside light measuring method, a color temperature is directlydetected by a color temperature sensor. A white balance control signalfor a red signal and a white balance control for a blue signal areproduced based on reference data detected by the color temperaturesensor in order to control the white balance. The color temperaturesensor is integrally formed with photosensors, for example, a photosensor with a red filter, a photo sensor with a Green filter and a photosensor with a blue filter. The white balance control for the blue signalare produced by an output voltage of each photo sensor, respectively.

In the inside light measuring method, a color temperature is indirectlydetected by a color temperature sensor. If a white balance is matchingin a picture, an averaged color of whole colors in a picture becomesachromatic color (Grey). The inside light measuring method utilizes thistheory. That is, an integrated averaged value of color differencesignals R-Y and B-Y at a reference color temperature that an averagedcolor for all of the colors in a picture becomes an achromatic color isdesignated as a reference value for each signal. Thus, gains of the redsignal and the blue signal are controlled in order to match theintegrated averaged value with the reference value.

The above described values of the white balance control for a red signaland the white balance control for a blue signal are calculated by adevice, such as a microcomputer and then white balance control signalsfor a red signal and a blue signal are output from the microcomputer toa white balance circuit. In the white balance circuit, gains of a redsignal and a blue signal are controlled based on values of the whitebalance control signals.

On the other hand, in a manual white balance method, an operator detectsa kind of light source (for example, sunshine, electric bulb,fluorescent lamp and so on) in a photographing field by himself and thenthe operator selects the kind of the light source by manually operatinga device for selecting a light source, such as a switch. In accordancewith a selection of the light source, gains of the red signal circuitand the blue signal circuit are set at specific Gains corresponding tothe kinds of the light sources.

The condition in which an averaged color becomes an achromatic color(grey) in a picture is achieved when the video camera takes a photographof an ordinal sight in which various colors are mixed randomly. However,when the video camera takes a photograph of an object having abackground of a blue sky, a blue ocean or a red wall, the abovedescribed condition cannot be accomplished. An averaged color for all ofthe colors in a picture is not an achromatic color, the averaged colorbecomes a color with a blue tint or a red tint. If the video cameratakes a photograph of a sight dominated by a mono-colored background,the averaged color of the picture is recognized as the achromatic colorby a white balance control in the inside light measuring method,although an averaged color in a picture is not an achromatic color. As aresult, a reference white level is only slightly different from the truewhite level. The color of the background is discolored and a color of amain object (person) is controlled to be shifted to its additivecomplementary color (additive complementary color against thebackground), and a so called "color failure" occurs.

As a result, in an inside light measurement control, a video camera witha white balance control unit takes a photograph of an ordinal sight inwhich various colors are mixed randomly, so that the white balancecontrol is operated properly. On the other hand, when the video cameratakes a photograph of a specific sight in which a specific colordominates, the above described color failure occurs.

In a conventional automatic white balance control device, white balancecontrol signals are output with predetermined intervals. If thepredetermined intervals of the output white balance control signals aretoo short, the white balance control signals are not accuratelyconverged by the occurrence of hunting. On the other hand, if thepredetermined intervals of the output balance control signals are toolong, the device spends a large amount of time to converge, although thewhite balance control signals are accurately converged. Therefore, someof the following problems arise for example. Such as, if a colortemperature is suddenly changed or a light source is turned on, thedevice needs to spend a long time for operating white balance normallyin the case when the white balance control signals should be convergedas early as possible.

In the above described conventional manual white balance method, gainsof the red signal circuit and the blue signal circuit are set to thespecific value which depends on the kinds of the light sources. Even ifthe same kind of the light source is selected, a deterioration ofreproduced colors occurrs by a difference between a predetermined valueof a selected light source and an actual color temperature, becausethere are various fluorescent lamp types and colors associated with acamera which have undesirable influences.

OBJECTS OF THE PRESENT INVENTION

Upon reviewing the conventional art, one object of the present inventionis to provide a white balance control device for photographing a sightin which one specific color dominates without color failure occurring.

Another object of the present invention is to provide a white balancecontrol device for photographing a sight in which one specific colordominates without color failure occurring, and particularly to a whitebalance control device for properly controlling white balance when anobject is photographed under a light source or without a light source.

A further object of the present invention is to provide a white balancecontrol device for accurately controlling white balance simultaneouslywith shortening a converging period.

A still further object of the present invention is to provide a whitebalance control device for photographing a sight in which one specificcolor dominates without color failure occurring, and particularly to awhite balance control device for properly controlling white balance whenan object is photographed indoors or outdoors.

Another object of the present invention is to provide a white balancecontrol device for properly controlling white balance with a manualoperation.

SUMMARY OF THE INVENTION

To accomplish the above objects, a white balance control device in aninside light measurement control method of an embodiment of the presentinvention comprises

white balance control means for controlling white balance by controllingan amplification degree of a red elementary color signal and a blueelementary color signal of red-, green-, and blue- elementary colorsignals,

color matrixing means for outputting first and second color differencesignals by processing first and second the elementary color signal whitebalance controlled by said white balance control means,

processing means for detecting a brightness of an object simultaneouslywith transmitting white balance control signals to the white balancecontrol means, wherein the white balance control means is actuated inorder to equalize integral averaged values of the first and second colordifference signals, and reference values and predetermined integralaveraged values for each first and second color difference signal areset as the reference values when an averaged color of all colors in apicture becomes an achromatic color at a reference color temperature,and

controlling means for stepping up and down values of the white balancecontrol signals after a battery source is turned on and values of thewhite balance control signals converge in a condition that the values ofthe white balance control signals are varied within a variable region ofwhich a center point is the previous converged value or a value of aprevious fixed time, when the differences between the integral averagedvalues for the first and second color difference signals and thereference values are more than predetermined values and a presentbrightness value is changed more than a predetermined value with respectto a value of the previous brightness or a brightness at a previousfixed time,

wherein the processing means fixes the values of the white balancecontrol signals while the stepped up and down values of the whitebalance control signals become a boundary value or the values of thewhite balance control signals are fixed or converged within the variableregion, and the variable region is renewed to a new variable region ofwhich a center point is the present fixed values or present convergedvalues.

A white balance control device of another embodiment of the presentinvention comprises processing means for detecting whether aphotographing condition is suitable for a telescope condition or a widecondition and narrowing a variable region in the telescope condition andenlarging the variable region in the wide condition.

To accomplish the above object, a structure of a white balance controldevice of a different embodiment in an inside light measurement controlmethod of the present invention comprises

white balance control means for controlling white balance by controllingan amplification degree of a red elementary color signal and a blueelementary color signal out of red-, green-, and blue- elementary colorsignals,

color matrixing means for outtputing first and second color differencesignals by processing elementary color signals white balance controlledby said white balance control means,

processing means for transmitting white balance control signals to thewhite balance control means, wherein the white balance control means isactuated in order to equalize integral averaged values of the first andsecond color difference signals, and reference values and predeterminedintegral averaged values for each first and second color differencesignals are set as the reference values when an averaged color of allcolors in a picture becomes an achromatic color at a reference color,

controlling means for inputting zoom information after a battery sourceis turned on and a value of white balance control signals converges,wherein the processing means increases the reference values when azooming position is in a telescope condition or a brightness value of anobject is high, the processing means decreases the reference values whenthe zooming position is in a wide condition or the brightness value ofan object is low so that a recognize level for changing a brightnessvalue can be determined and the values of the white balance controlsignals are changed in order to equalize the integral averaged values ofeach first and second color difference signal and the respectivereference values when a difference between a present brightness valueand a brightness value at the last converged time is more than therecognize level for changing the brightness value.

To accomplish the above objects, a structure of a white balance controldevice of another embodiment of the present invention comprises

white balance control means for controlling white balance by controllingan amplification degree of a red elementary color signal and a blueelementary color signal out of red-, green-, and blue- elementary colorsignals,

color matrixing means for outputting first and second color differencesignals by processing elementary color signals white balance controlledby said white balance control means, and

processing means for transmitting white balance control signals to thewhite balance control means, wherein the white balance control means isactuated in order to equalize integral averaged values of the first andsecond color difference signals, and reference values and predeterminedintegral averaged values for each first and second color differencesignal are set as the reference values when an averaged color of allcolors in a picture becomes an achromatic color at a reference colortemperature,

the processing means outputting an interval of a white balance controlsignal of which a value is changed by one step value longer after adifference between the integral averaged values of the first and secondcolor difference signals and the reference values are less than apredetermined level for changing or values of the white control signalsare converged once.

To accomplish the above objects, a structure of a white balance controldevice of a different embodiment in an inside light measurement methodof the present invention comprises,

brightness detecting means for detecting a brightness value of an objectand for selecting an outdoor mode for phtographing properly outdoorswhen the brightness value of the object is higher than a level forchanging modes, and an indoor mode for photographing properly indoorsunder an artificial light such as a fluorescent lamp and an incandescentlamp when the brightness of the object is less than the level forchanging modes, controlling means for controlling white balance within aselected restricted region by detecting a color temperature of sunshinein the outdoor mode and white balance within a selected restrictedregion by considering a color temperature of the respective artificallight in the indoor mode, and after the values of white balance controlsignals converged to a value corresponding to the outdoor mode, andchanging means for changing values of white balance control signals to avalue corresponding to the indoor mode after the values of the whitebalance control signals converge to a value corresponding to theoutdoors mode when a brightness value of an object is less than a valuefor mode changing and the differences between integral averaged valuesof the first and second color difference signals and the referencevalues are more than a level for detecting an expanding/convergingvalue, and changing values of the white balance control signals to avalue corresponding to the outdoor mode after the values of the whitebalance control signals converge to a value corresponding to the indoormode when a brightness value of an object is higher than a value forchanging and differences between the integral averaged values of thefirst and second color difference signals and the reference values aremore than a level for detecting the expanding/converging value.

To accomplish the above objects, a structure of the white balancecontrol device of a different embodiment of the present inventioncomprises,

light source selecting means for manually selecting light sources,

white balance control means for controlling an amplification degree of ared elementary color signal and a blue elementary color signal out ofred, green and blue elementary color signals,

color matrixing means for outputing first and second color differencesignals by processing white balance controlled elementary color signalsby said white balance control means, and

processing means for transmitting white balance control signals to thewhite balance control means, wherein the white balance control means isactuated in order to equalize integral averaged values of the first andsecond color difference signals and reference values and predeterminedintegral averaged values for each color difference signal are set as thereference values when an averaged color of all colors in a picturebecomes an achromatic color at a reference color temperature,

the processing means determining outputs of initial values of the whitebalance control signals and a variable region in order to control thevalues of the white balance control signals within the variable region.

In the present invention, values of white balance control signals arechanged step by step when differences between integral averaged valuesof color difference signals and the reference values are more than thepredetermined level value and a brightness value of an object is changedmore than a predetermined level with a movable area of the values beingrestricted within the variable region.

In the present invention, values of white balance control signals arechanged in order to equalize integral averaged values of colordifference signals and the reference values when a difference between apresent brightness value and a brightness value at the last convergedtime is more than a recognition level for changing brightness. Inaddition,

(i) if a zooming position is in a telescope condition, the recognizinglevel for changing brightness is relatively high and if a zoomingposition is in a wide condition, the recognition level for changingbrightness is relatively low, and

(ii) if a brightness value of an object is high, the recognition levelfor changing brightness is relatively large and if the brightness valueof an object is low, the recognition level for changing brightness isrelatively low.

In the present invention, the values of the white balance controlsignals can be rapidly and accurately converged by controlling theoutputting intervals of the white balance control signals. That is, ifthe outputting intervals become shorter, a converging time can beshortened. If the outputting intervals become longer, the values of thewhite balance control signals can be converged accurately.

The spectral characteristics of natural light and the spectralcharacteristics of artificial light are quite different from each other.Therefore, it is necessary to widen the controllable area in order tocontrol white control corresponding to both kinds of light sourcesbecause color failure sometimes occurs. On the contrary, if thecontrollable area is narrowed in order to prevent color failure fromoccurring, it is insufficient to control white balance.

On the other hand, in the present invention, the controllable area isseparated to an area for an outdoor mode and an area for an indoor modeso that white balance control is properly operated in both modes. Sincethe controllable area is restrictly specified, for example, even ifgreen grass is photographed outdoors, white balance is controlledproperly without over adjusting to have color failure occur. Switchingthe area of the outdoor mode and the area of the indoor mode isdetermined by the brightness value of an object and differences betweenthe integral averaged values of color difference signals and thereference values, so that the switching is done accurately.

In the present invention, the amplification degree of the red signal andthe blue signal does not have a fixed gain thereof. Values of whitebalance control signals are limited within some region and are changedin order to equalize the integral averaged values of the colordifference signals and the reference value. Thereby, in a manual whitebalance method, even if there are differences between the predeterminedcolor temperature of a selected light source and the actual colortemperature of the selected light source, it is possible to preventdeterioration of reproduced colors without ignoring an operator'sselection of a light source.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the present invention, and wherein:

FIG. 1 shows a block diagram of a video camera according to anembodiment of the present invention;

FIG. 2 shows initial values of white balance control signals and theirvariable region;

FIG. 3 shows a flow chart for the operation of a first embodimentaccording to the present invention;

FIG. 4 shows values of white balance control signals at an initialphotographing time;

FIG. 5 shows white balance control signals and their variable region;

FIG. 6 shows a variation of white balance control signals;

FIG. 7 shows variation of white balance control signals and its renewedcondition of a variable region;

FIG. 8 shows a condition of converging the white balance controlsignals;

FIG. 9 shows a flow chart for the operation of a second embodiment ofthe present invention;

FIG. 10 shows a flow chart for the operation of a third embodiment ofthe present invention;

FIG. 11 shows a flow chart for the operation of a fourth embodiment ofthe present invention;

FIG. 12 shows a relation between the brightness value of an object and arecognize level for changing brightness;

FIG. 13 shows a flow chart for the operation of a fifth embodiment ofthe present invention;

FIG. 14 shows a flow chart for the operation of a sixth embodiment ofthe present invention;

FIG. 15 shows a control region of a control device;

FIG. 16 shows a flow chart for the operation of a seventh embodiment ofthe present invention; and

FIG. 17 shows a flow chart for the operation of an eighth embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments for the present invention will be described withreference to drawings as follows.

FIG. 1 shows a block diagram of a video camera of the first embodimentof the present invention. Although each operation as claimed in therespective claims are different from each other, the structure of thevideo camera is common. The equipment structure will be explained first.As shown in FIG. 1, a picture image of an object is formed by a lens 1and the picture image is input to a charge coupled device (CCD) 3through an iris. Additive complementary color (cyanogen, magenta,yellow, green) filters are provided at an image pick up surface of thecharge coupled device 3. A charge signal E indicates that the object isinput to a signal processing circuit 5 through a sample hold (S/H) andautomatic gain control (AGC) circuit 4. The signal processing circuit 5outputs a brightness signal Y and elementary color signals R, G and B byprocessing the charge signal E. The elementary color signals R, G and Bare white balance controlled in a white balance control device 6,γ--adjusted in a γ adjustment circuit and input to a matrix circuit 8.In the matrix circuit 8, the elementary color signals R, G and B arematrix processed and the color difference signals are output. In anencoder 9, the color difference signals are orthogonally two phasemodulated and the brightness signal Y is added to the signals and thenthe signal is output as a video signal by the NTSC method.

An output from the S/H and AGC circuit 4 is digitally converted in ananalog/digital (A/D) convertor 18, integrated in an integral circuit 19and then input to a microcomputer 10. In the microcomputer 10, an AGCcontrol signal is transmitted to the S/H and AGC circuit 4 through adigital/analog converter 11 based on an integrated value output from theS/H and AGC circuit 4. In the microcomputer 10, a zoom information P1 istransmitted from a lens driver and an iris data P2 for indicating anopening degree of an iris is transmitted from a hole element 12 fordetecting an iris degree.

The microcomputer 10 computes a brightness of an object based on theopening degree of the iris 2, the gain and the electronic shutter speedfrom the S/H and AGC circuit 4. That is, the higher that the brightnessof an object becomes, the narrower that an opening degree of the iris 2becomes. On the other hand, the lower that the brightness of an objectbecomes, the wider that an opening degree of the iris 2 becomes. Whenthe iris 2 is opened, the lower that the brightness of an objectbecomes, the greater that a gain of the S/H and AGC circuit 4 becomes.At that time, when the electronic shutter is actuated at high speed, theopening degree of the iris 2 and the gain information from the S/H andAGC circuit 4 becomes dark. The microcomputer 10 computes thisinformation so that the brightness of the object can be detected.

On the other hand, the color difference signals R-Y and B-Y output fromthe matrix circuit 8 is averaged in low pass filters 13 and 14. Thesignals are converted to digital signals in analog/digital converters 15and 16 and then output to the microcomputer 10, respectively. In themicrocomputer 10, integral averaged values of the color differencesignals R-Y and B-Y, which are computed in a condition that an averagedcolor of all colors at a reference color temperature, are designated asreference values, respectively.

A white balance control signal (Rcont) for a red signal, which equalizesthe integral averaged value of the color difference signals R-Y and thereference value of the color difference signal R-Y, and a white balancecontrol signal (Bcont) for a blue signal, which equalizes the integralaveraged value of the color difference signal B-Y and the referencevalue of the color difference signal B-Y, are output from themicrocomputer 10. The signals Rcont and Bcont are analog converted in adigital/analog converter 17 and then transmitted to the white balancecontrol devices 6. In the white balance control device 6, the gain of anelementary red color signal R and an elementary blue color signal B iscontrolled in accordance with the value of the white balance controlsignals Rcont and Bcont, respectively and a feed back control of thewhite balance is actuated. A timing and an area of the white balancecontrol with respect to the white balance control signals Rcont andBcont will be described.

A device for manually selecting a light source with a switch 20 isconnected to the microcomputer 10. The switch 20 can select three kindsof light soruces, that is, sunshine, electric bulb and fluorescent lamp.As shown in FIG. 2, in accordance with the selected light source, aninitial value r-0 of a white balance control signal Rcont for a redcolor signal, an initial value b-0 of a white balance control signalBcont for a blue color signal and a variable area β for these controlsignals Rcont and Bcont are preset in the microcomputer 10 correspondingto each kind of light source.

The first embodiment of the present invention will be described nextwith an explanation for the operation of the microcomputer 10. As shownby a flow chart in FIG. 3, a battery source is turned on in a step 1 andthen an initial operation for white balance control is actuated in astep 2. As shown in FIG. 4, at first, a value r-0 as a white balancecontrol signal Rcont for a red signal and a value b-0 as a white balancecontrol signal Bcont for a blue signal are output from the microcomputer10. The values r-0 and b-0 are preset values. Then, integral averagedvalues of white balance controlled color difference signals R-Y and B-Y,which correspond to the values r-0 and b-0 of the white balance controlsignals Rcont and Bcont, are input to the microcomputer 10 and theintegral averaged values of the color difference signals and thereference values are compared. As a result of the comparison, ifdifferences between the integral averaged values of the color differencesignals and the reference values are more than predetermined values, thevalues of the white balance control signals Rcont and Bcont are steppedup or down and then output. The values of the white balance controlsignals Rcont and Bcont are successively stepped up or down and thenoutput until the differences between the integral averaged values of thecolor difference signals and the reference values are less than thepredetermined values. When the differences are less than thepredetermined values (for example, 10LSB [Least Significant Bit]), thevalues of white balance control signals Rcont and Bcont become constant,which is called "converging".

FIG. 5 shows step values r-1 and b-1 of the white balance controlsignals Rcont and Bcont, which are stepped up four times from theinitial values r-0 and b-0 of the white balance control signals Rcontand Bcont as shown in FIG. 4.

The values of the white balance control signals Rcont and Bcont areincreased or decreased step by step. Therefore, eight variations can beobtained by changing at least one of the values one step toward one ofthe bidirections as shown in FIG. 6.

Again as shown in FIG. 3, after the initial operation is finished,present values r-1 and b-1 (c.f. as shown in FIG. 5) of the whitebalance control signals Rcont and Bcont are memorized and a brightnessvalue at a converged time is detected and then memorized in a step 3.Further, a variable region α as shown in FIG. 5 is determined. In thisexample, an upper boundary line and a lower line of the variable regionα is determined by increasing or decreasing the converged value b-1 foursteps, respectively. A right end boundary line and a left end boundaryline of the variable region α is determined by increasing or decreasingthe converged value r-1 four steps, respectively.

The integral averaged values of the color difference signals are inputin a step 4. It is judged whether or not differences between theintegral averaged values and the reference values are less than thepredetermined value in a step 5. If the differences are more than thepredetermined value, it means that the white balance control isimproper. Then, in a step 6, it is computed whether the values of thewhite balance control signals Rcont and Bcont should be increased ordecreased in order to control white balance properly.

In a step 7, it is judged whether a displacement of the presentbrightness is more than the predetermined value (for example, 0.4BV:Brightness Value) with respect to a previously memorized brightnessvalue (memorized in the step 3). If a displacement amount is more thanthe predetermined value, it is considered that an object is changed andthe operation goes to a step 8. One of the characteristics of thepresent, embodiment is to detect whether an object is changed or not inresponse to a displacement of the brightness value of an object.

In the step 8, it is detected whether the present values of the whitebalance control signals Rcont and Bcont are within a predeterminedvariable region α. If the values are within the variable region α, theoperation goes to a step 9. In the step 9, the values of the whitebalance control signals Rcont and Bcont, which are increased ordecreased by one step, are output. In the step 6, it is alreadydetermined whether the values are increased or decreased.

By repeating a control operation of the steps 4, 5, 6, 7, 8 and 9 in theflow chart, the values of the white balance control signals Rcont andBcont are successively changed. FIG. 7 shows that the values of thewhite balance control signals Rcont and Bcont are successively steppedup three times and changed from the values r-1, b-1 to the values r-2,b-2 by repeating the operation control of the steps 4 through 9 in theflow chart.

On the other hand, for example as shown in FIG. 7, when the values ofthe white balance control signals Rcont and Bcont are converged at thevalues r-2 and b-2, that is, the difference is determined to be lessthan the predetermined value in the step 5 in the flow chart of thecontrol operation as shown in FIG. 3, the operation returns to the step3. In the step 3, the converged values r-2 and b-2 of the white balancecontrol signals Rcont and Bcont are memorized and the brightness valueat the time are memorized. Further, a new variable region α-1 isdetermined. An upper boundary line and a lower boundary line of the newvariable region α-1 are determined by increasing and decreasing theconverged step value b-2 by four steps, respectively. A right endboundary line and a left line boundary line of the new variable regionα-1 are determined by increasing and decreasing the converged step valuer-2 by four steps, respectively. Thus, a variable region is renewed fromthe region α to the region α-1.

In the present embodiment, as shown in FIG. 8, when the values r-1 andb-1 of the white balance control signals Rcont and Bcont are changed tothe values r-3 and b-3 by stepping up four times and the values r-3 andb-3 become border values of a variable area α, the values of the whitebalance control signals are fixed without varying, although a differencebetween integral averaged values of the color difference signals and thereference values are more than the predetermined values. In the flowchart as shown in FIG. 3, an operation does not go to the step 9 in thecase when it is determined that the values of Rcont and Bcont are notwithin a variable region in the step 8. If the values of the whitebalance control signals become the boundary values of the variable area,the values of the white balance control signals are fixed although thedifferences between the integral averaged values of the color differencesignals and the reference values are more than the predetermined values.It is a so called "fixing" that the values of the white balance controlsignals Rcont and Bcont are controlled not to be changed when the valuesbecome the boundary values. In case of the "fixing" and the"converging", the values of the white balance control signals are notchanged. In the case of the fixing, the differences between the integralaveraged values of the color difference signals and the reference valuesare more than the predetermined values. In the case of the converging,the differences are less than the predetermined values.

If it is determined that the values of Rcont and Bcont are not within avariable region in the step 8 and the values of the white balancecontrol signals Rcont and Bcont are fixed, the operation returns to thestep 3. In the step 3, the fixed values (r-3, b-3 as shown in FIG. 8) ofthe white balance control signals Rcont and Bcont are memorized and thebrightness value at the time is also memorized, and a new variableregion α-2 having a horizontal width equalizing with+four step value anda vertical length equalizing with+four step value with respect to stepvalues r-3 and b-3.

In an embodiment according to the present invention, a movable area ofthe values of the white balance control signals Rcont and Bcont isrestricted and specified within the variable area. Even if amono-colored object is suddenly photographed, the values of the whitebalance control signals Rcont and Bcont are not significantly changed.Therefore, an occurrence of color failure can be prevented. This featureis one of the most important characteristics of the present embodiment.A practical photographic action will be described as follows.

In the step 7 as shown in FIG. 3, if it is judged that brightness valueis not changed by more than the predetermined value from the value atthe previous converged time or the brightness value at the last fixedtime, the operation returns to the step 4.

The practical photographic action with reference to the flow chart ofthe control operation as shown in FIG. 3 will be explained. For example,a beach side is photographed at first and then a bright blue ocean isphotographed.

When turning on a battery switch at a beach side, the values of thewhite balance control signals Rcont and Bcont are converged by initiallyoperating white balance control (steps 1 and 2). The converged valuesand the brightness at the beach side are memorized and then a variableregion is specified.

Generally, the white balance control at the beach side is notsignificantly changed. When the operation goes to the step 5, thedifference is determined to be less than the predetermined value.Therefore, the operation does not go to the step 9 and the values of thewhite balance control signals Rcont and Bcont are not changed. If a redswimming wear is photographed, the differences between the integralaveraged values of the color difference signals and the reference valuesbecome large and the difference is determined to be greater than thepredetermined value in the step 5. However, it is determined that thebrightness value does not change by a predetermined amount in the step 7in the case that a displacement of the brightness is less than thepredetermined value as a result, the operation does not go to the step 9so that the values of the white balance control signals Rcont and Bcontare not changed and color failure does not occur.

If a bright blue ocean is rapidly photographed for a whole scope of apicture, the differences between the integral averaged values of thecolor difference signals and the reference values become large and thedifference is determined to be greater than the predetermined value inthe step 5. If the brightness value of the ocean becomes much higherthan the brightness value of the beach side and the brightness value isdetermined to change by a predetermined amount in the step 7, the stepvalues of the white balance control signals Rcont and Bcont are steppedup (down) one time and output in the step 9. After repeating the steps 4through 9 several times, the values of the white balance control signalsRcont and Bcont become boundary values and the values of Rcont and Bcontare determined to be outside of the variable region in the step 8, andthe values of the white balance control signals Rcont and Bcont arefixed without going to the step 9.

As described above, although a difference between the integral averagedvalues of the color difference signals to be photographed for a blueocean in a full scope of a picture and the reference values are large,the values of the white balance control signals Rcont and Bcont arefixed when the values become the boundary values of the variable region.Thus, even if a blue ocean is photographed, the values of the whitebalance control signals Rcont and Bcont are not significantly changedand color failure does not occur.

Unless the variable region is predetermined, the values of the whitebalance control signals Rcont and Bcont are changed by a large amount.Although an averaged color of all colors in a picture is blue, theaveraged color is recognized as an achromatic color and the whitebalance control is operated so that a blue ocean becomes grey and colorfailure occurs.

A structure of the first embodiment of the present invention specifies avariable region so as to provide a limit of the displacement of thevalues of the white balance control signals Rcont and Bcont.

When an ocean is photographed, the fixed values of the white balancecontrol signals Rcont and Bcont and the brightness of the ocean arememorized and then a new variable region is determined with respect tothe memorized values (step 3). In the step 7, the brightness value isdetermined not to change by a predetermined amount, since the oceanbrightness value at this time is the same as the ocean brightness valueat the previous time. The operation does not go to the step 9 and thevalues of the white balance control signals Rcont and Bcont are notchanged.

Next, the second embodiment according to the present invention will bedescribed with respect to FIG. 9. In comparison with the firstembodiment according to the present invention (as shown in FIG. 3), thesteps of the second embodiment of the present invention are the same asthe steps of the first embodiment of the present invention except forthe addition of a step 2-1.

In the step 2-1 as shown in FIG. 9, zoom information P1 is input. Whenthe camera is shifted to a telescope condition, an area of the variableregion determined in the step 3 becomes narrow (for example, the widthand the length of the variable region are+2 step value). When the camerais shifted to a wide condition, an area of the variable regiondetermined in the step 3 becomes normal space (for example, the widthand the length of the variable region are+4 step value).

A reason why the variable region becomes narrow in the telescopecondition is as follows. When photographing in the telescope condition,a picture would be dominated by one object. If the color of the objectis mono-color, it is recognized that a color temperature is changed andcolor failure occurs although the color temperature does not change.Therefore, the camera is shifted to a telescope condition, anddisplacement values of the white balance control signals are strictlyspecified by narrowing the variable region in order to prevent the colorfailure from occuring.

Next, the third embodiment according to the present invention along adescription of an operation of the microcomputer 10 will be described.As shown in a flow chart in FIG. 10, a battery source is switched on ina step 101 and an initial operation of the white balance control isactuated in a step 102. The initial operation is the same as the step 2shown in FIG. 3.

After finishing the initial operation, the operation goes to a step 103and the zoom information is input. Next, in a step 104, the presentvalues r-1 and b-1 (see an example as shown in FIG. 5) of the whitebalance control signals Rcont and Bcont are memorized simultaneouslywith memorizing the brightness value at a converging time. Further, asshown in FIG. 5, a variable region α is determined. A recognition levelfor changing the brightness value is specified corresponding to the zoominformation.

The recognition level for changing brightness will be explained asfollows.

(1) In the telescope condition, the recognition level for changing thebrightness value is 0.8Bv (Brightness value) with respect to a plusdirection and 1.4Bv with respect to a minus direction.

(2) In the wide condition, the recognition level for changing thebrightness value is 0.4Bv with respect to a plus direction and 0.8Bvwith respect to a minus direction.

The value of the recognition level for changing brightness increasesslightly from the wide condition to the telescope condition.

In a step 105, the color difference signals are input and it is judgedwhether the differences between the integral averaged values of thecolor difference signals and the reference values are less than thepredetermined values in a step 106. If the differences are more than thepredetermined value, then the white balance is controlled improperly.Then, the operation goes to a step 107 and it is determined whether thevalues of the white balance control signals Rcont and Bcont should beincreased or decreased in order to control white balance properly.

In a step 108, it is judged whether a difference between the presentbrightness value and the previous memorized brightness value (memorizedin the step 104) is more than the recognition level for changingbrightness detected in the step 104. If the difference is more than therecognition level for changing brightness, it is judged that an objectis changed and an operation goes to a step 109.

If a following equation is assumed;

    (present brightness)+(previous memorized

    value)-(brightness value)=d,

(1) in the telescope condition, it is judged that an object is changedin the case that the difference d is more than 0.8Bv or less than-1.4Bv, and

(2) in the wide condition, it is judged that an object is changed in thecase that the difference d is more than 0.4Bv or less than -0.5Bv.

The technique according to the third embodiment of the present inventionis on the premise that a change of an object is based detected by adisplacement of the brightness value of the object.

In a step 109, it is judged that the present values of the white balancecontrol signals Rcont and Bcont are within the variable region αdetermined in the step. 104. If the present values are within thevariable region α, the operation goes to a step 110. In the step 110,the values of the white balance control signals Rcont and Bcont arestepped up or down by one step and then output. The judgement of whetherthe values are increased or decreased is determined in the step 107.

While the control operation of the steps 105, 106, 107, 108, 109 and 110of the flow chart are repeated, the values of the white balance controlsignals Rcont and Bcont are successively changed. As shown in FIG. 7,the values of the white balance control signal Rcont are stepped upthree times and changed from the value r-1 to the value r-2 and thevalue of the white balance control signal Bcont is stepped up threetimes and changed from the value b-1 to the value b-2 by repeating thecontrol operation of the steps 105 through 110 of the flow chart threetimes.

On the other hand, when the values of the white balance control signalsRcont and Bcont are converged to the values r-2, b-2, respectively, inFIG. 7, that is, the difference is determined to be less than apredetermined value in the step 106 in a flow chart as shown in FIG. 10,the operation returns to the steps 103 and 104 and the converged valuesof the white balance control signals Rcont and Bcont r-2, b-2 arememorized and the brightness value at the time is also memorized.Further, a new variable region 4-1 having a±four step horizontal widthand a±four step vertical length with respect to the step values r-2 andb-2 is used as a central point. That is, the variable region is renewedfrom the region α to the region α-1. Further, the recognition level forchanging, which corresponds to the zoom information, is set again.

Further, in the embodiment according to the present invention, as shownin FIG. 8, in the case that the values of the white balance controlsignals Rcont and Bcont are positioned in the variable region α, whenthe values are stepped up four times, changed from the values r-1 andb-1 to the values r-3 and b-3 and become boundary values of the variableregion α, the values of the white balance control signals are fixedwithout changing, although the integral averaged values of the colordifference signals and the reference value are more than thepredetermined value. In the flow chart as shown in FIG. 10, the valuesof Rcont and Bcont are determined to be outside of the variable regionin the step 109 so that an operation does not go to the step 110. Asdescribed above, when the values of the white balance control signalsRcont and Bcont become the boundary values of the variable region, thevalues are fixed, although the differences between the integral averagedvalues for color difference signals and the reference values are morethan the predetermined values.

If the values of Rcont and Bcont are determined to be outside thevariable region and the values of the white balance control signalsRcont and Bcont are fixed in the step 109, the operation goes back tothe steps 103 and 104, the fixed values of the white balance controlsignals r-3 and b-3 (for example, in FIG. 8) are memorized and thebrightness values at the time is also memorized. A new variable regionα-2 is specified having a+four step horizonal width and a+four stepvertical length with respect to the step values r-3 and b-3 as a centralpoint of the variable region. The recognition level for changingbrightness is set again.

As described above, in the embodiment according to the presentinvention, the area where the values of the white balance controlsignals Rcont and Bcont can be varied is limited within a variableregion, so that the values of the white balance control signals Rcontand Bcont cannot be significantly changed, even if a mono-colored objectis suddenly photographed. Therefore, it is possible to prevent colorfailure from occurring.

In this embodiment according to the present invnetion, a recognitionlevel for changing brightness is changed depending on the telescopecondition and the wide condition. When the camera is shifted to thetelescope condition, the present brightness value is the brightnessvalue at the last converged time and the values of the white balancecontrol signals Rcont and Bcont are changed only when the brightnessvalues are significantly changed. When the camera is shifted to the widecondition, the brightness value is changed when the present brightnessvalue is changed by a small amount from the (fixed) value at the lastconverged time. The sensitivity for the brightness value is changedcorresponding to the telescope condition and the wide condition, whichis one of the most important features of the present embodiment.

As described above, a reason why the recognition level for changingbrightness becomes higher in the telescope condition in order to avoid achange of the values of the white balance control signals Rcont andBcont will be described as follows. When an object is photographed inthe telescope condition, a part of a picture may occassionally bedominated by one object. If a color of one object is mono-color, arecognition of changing the color temperature may be mistaken and colorfailure occurs, although the color temperature is not changed.Therefore, an object is determined to have changed only when thebrightness value is significantly changed in the telescope condition.Thus, the values of the white balance control signals Rcont and Bcontare changed and a recognition of changing color temperature is preventedfrom being mistaken. In a view of a different point, a displacement ofbrightness value in a whole scope of a picture in the telescopecondition is generally larger than the displacement of the brightnessvalue in the wide condition. Therefore, in the telescope condition, therecognition level for changing the brightness value is made higher.

In the step 108 as shown in FIG. 10, it is judged that a brightnessvalue is not changed more than a predetermined value from the brightnessvalue at the last converged time or the previous fixed value and thenthe operation retunrs to the step 105.

The fourth embodiment of the present invention will be explained nextwith reference to a flow chart as shown in FIG. 11. An operation of aflow chart as shown in FIG. 11 is the same as the operation control ofthe flow chart as shown in FIG. 10 except for the operation of steps 103and 104. The differences of these steps will be described.

After a battery source is switched on and an initial operation of thewhite balance control is finished (steps 101, 102), a brightness data ofan object is input in the step 103 and a recognition level for changingbrightness corresponding to the brightness value of the object isspecified in the step 104.

FIG. 12 shows a relation between the brightness value of an object and apredetermined recognition level for changing brightness. As shown inFIG. 12, in the embodiment according to the present invention, if thebrightness value of the object is more than L1, the recognition levelfor changing brightness is set as B1. If the brightness value of theobject is less than L1, the recognition level for changing brightness isset as 0.

The recognition level for changing brightness is set as shown in FIG.12, so that variations of changing the values of the white balancecontrol signals Rcont and Bcont are divided to two variations on aborder of the brightness value of the object L1 in the presentembodiment.

(1) When the brightness value of the object is equal to or more than L1,a difference between integral averaged values of color differencesignals and the reference values is more than the predetermined valuesand the white balance control is operated improperly (the decision isjudged to be YES in the step 106). When a difference between the presentbrightness value and a brightness value at the previous converged time(or the last fixed brightness value) is more than β1 (the decision isjudged to be YES in the step 108), the values of the white balancecontrol signals Rcont and Bcont are changed by one step value and thenoutput (step 110), while the values are in a variable region (thedecision is judged to be YES in the step 109). As a result, if thebrightness value is much more than the value L1, an object is recognizedas being changed and the values of the white balance control signalsRcont and Bcont are changed on a premise that the other conditions aresatisfied.

(2) On the other hand, when the brightness value of the object is lessthan L1, the decision is always judged to be YES in the step 108. Ifdifferences between integral averaged values of the color differencesignals and the reference values are more than the predetermined values(the decision is judged to be NO in the step 106), and the values of thewhite balance control signals Rcont and Bcont are within a variableregion (the decision is judged to be YES in the step 109), that is, ifthe two conditions are satisfied, the values of the white balancecontrol signals Rcont and Bcont are changed. As a result, if thebrightness value of the object is less than L1, the values of the whitebalance control signals Rcont and Bcont are changed on a premise thatthe above described two conditions are satisfied (steps 106, 109) andthe detection of a change of the brightness value of an object isstopped because a photographic circumstance is dark and it becomesdifficult to detect a change of the brightness value of an object.Accordingly, even if the photographic circumstance is dark, whitebalance control is always operated properly.

A control operation of the fifth embodiment will be explained nextaccording to the present invention with reference to FIG. 13. A batterysource is switched on in a step 201, and a value of the white balancecontrol signal for a red signal as an initial value and a value of awhite balance control signal for a blue signal as an initial value areoutput from the microcomputer 10. Accordingly, the initial values arepreset. Next, the microcomputer 10 inputs integral averaged values forcolor difference signals which are white balance controlled depending onthe values of the white balance control signals Rcont and Bcont as theinitial values in a step 203. In a step 204, it is judged whetherdifferences between the integral averaged values of the color differencesignals and the reference values are more than the predetermined values(for example, 10LSB [Least Significant Bit]). If the judgement is NO, itis recognized that the values are not converged and the operation goesto a step 205. In the step 205, it is computed whether the values of thewhite balance control signals Rcont and Bcont should be increased ordecreased in order to control white balance.

In a step 206, it is judged whether the differences between integralaveraged values of the color difference signals and the reference valuesare more than switching values. The switching values are more than thepredetermined values determined in the step 204. If the differencesbetween the integral averaged values and the reference values are morethan switching values, the operation goes to a step 207 and the valuesstepped up (down) once of the white balance control signals Rcont andBcont are output because the values of the white balance control signalsRcont and Bcont are quite different from the converged values.

When the values of the white balance control signals Rcont and Bcont aredifferent from the converged values and the difference between theintegral averaged values of the color difference signals and thereference values are more than the switching values, the steps 203through 207 of the control operation are repeated and values of thewhite balance control signals Rcont and Bcont renewed at intervals of0.5 second are output. Thus, the values of the white balance controlsignals Rcont and Bcont are renewed by intervals of a short period andthen output, so that the values will quickly converge.

As the value of the white balance control signals Rcont and Bcontapproach the converged values and the differences between the integralaveraged values of the color difference signals and the reference valuesbecome less than the switching value (the decision is judged to be NO ina step 206), the number of the cases is counted up in a step 208. Unlessthe number of the cases that the difference is less than the switchingvalue becomes a predetermined number of times (for example, four times),the operation goes to a step 207 and the values of the white balancecontrol signals stepped up (down) by one time value are output and thecounted times are reset.

As a result, when the values of the white balance control signals Rcontand Bcont approach the converged values, the output of the white balancecontrol signals Rcont and Bcont are thinned out and output intervalsbecome longer. Thus, the values can be converged accurately without theoccurrence of any hunting.

If the differences between the integral averaged values of colordifference signals and the reference values are more than thepredetermined values, that is, if the decision is judged to be YES inthe step 204, the operation returns to the step 203. In this case, thevalues of the white balance control signals Rcont and Bcont are renewed.

The sixth embodiment of the present invention will be explained next. Inthe present embodiment, after the values are converged once, aconverging speed becomes late by making the intervals for outputting thewhite balance control signals Rcont and Bcont longer.

A control operation of the sixth embodiment of the present inventionwill be explained with reference to FIG. 14. When a battery source isswitched on in a step 301, an initial operation of white balance controlis actuated in a step 302. At first, the microcomputer 10 outputs avalue of a white balance control signal for a red signal Rcont as aninitial value and a value of a white balance control for a blue signalas an initial value so that the initial values are preset. Next, themicrocomputer 10 inputs integral averaged values of color differencesignals white balance controlled corresponding to the white balancecontrol signals Rcont and Bcont as the initial values, respectively andthese values are compared with the integral averaged values of the colordifference signals and the reference values. Upon comparing the values,if the differences between the integral averaged values of the colordifference signals and the reference values are more than thepredetermined values, the values of the white balance control signalsRcont and Bcont stepped up (down) by one step value (increased ordecreased) are output. If the differences between the integral values ofthe color difference signals and the reference values are less than thepredetermined values (for example, 10LSB [Least Significant Bit]), thevalues of the white balance control signals Rcont and Bcont becomeconstant.

In the initial operation as described above, in the case that intervalsfor outputting the white balance control signals Rcont and Bcont arefixed at 0.5 second, the intervals may become shorter when the valuesare much different from the converged value and the intervals may becomelonger when the values become the same as the converged values.

After the values converge once, the integral averaged values of thecolor difference signals during a photographing period are input in astep 303. In a step 304, it is judged whether the difference between theintegral averaged values of the color difference signals and thereference values are less than the predetermined values. If the decisionis judged to be YES, the white balance is controlled properly, theoperation returns to the step 303 and the present values of the whitebalance control signals are maintained. If the decision is judged to beNO, the white balance is controlled imporperly, and the operation goesto a step 205. In the step 305, a number of cases that the difference ofthe integral averaged values and the reference values are more than thepredetermined value is counted.

In a step 306, it is judged whether the counted number approaches thepredetermined count number (for example, four times). If the decision isjudged to be NO, the operation returns to the step 303 and the presentvalues of the white balance control signals are maintained. If thedecision is judged to be YES, varying directions of the value of thewhite balance control signals Rcont and Bcont are computed in a step 307and the value stepped up (down) by one step value of the white balancecontrol signals Rcont and Bcont are output in the step 308.

Until the detecting number of the changed color temperatures becomes thecount number, the values of the white balance control signals Rcont andBcont are not renewed. Accordingly, even if a mono-colored object isphotographed in a full scope of a picture, the values of the whitebalance control signals Rcont and Bcont are not changed and a properwhite balance control can be maintained.

When the color temperatures are changed during a photographing period,the values of the white balance control are renewed only for a fewnumber of times. That is, after the values converge in the initialcondition once, it is seldom that the color temperatures changesuddenly. Thereby, the object can be photographed while the values ofthe white balance control are slightly changed. An occurrence of colorfailure which happens in the case that a mono-colored object isphotographed can be prevented as much as possible unless one object isphotographed for a long time.

Next, the seventh embodiment of the present invention will be described.In the seventh embodiment, an indoor mode and an outdoor mode are set ina microcomputer 10 as shown in FIG. 15. In the indoor mode, the valuesof the white balance control signals Rcont and Bcont are positionedwithin a region X surrounded with a real line in FIG. 15. When a whitepaper is photographed under an electric bulb, a cool white fluorescentlamp, a natural fluorescent lamp, and a day light fluorescent lamp,values of the white balance control signals Rcont and Bcont arepositioned at points A, B, C, and D, respectively as shown in FIG. 15.In the region X of the indoor mode, each of the converged values of thewhite balance control signals photographed on a white paper under arespective artificial light are included and the region X becomesnarrow. On the other hand, in the outdoor mode, the values of the whitebalance control signals Rcont and Bcont are positioned within a region Ysurrounded with a long and short dotted line in FIG. 15.

The microcomputer 10 detects brightness values of an object by judgingfrom an iris data P8 and judges the outdoor mode if the detectedbrightness value is more than a mode switching value and the indoor modeif the detected brightness value is less than the mode switching value.As shown in Table 1, the fact that an outdoor brightness value isgenerally more bright than an indoor brightness is used.

                  TABLE 1                                                         ______________________________________                                        unit                                                                          (lux)                                                                         ______________________________________                                        100,000    snow mountain                                                      (100,000)  sky slope                                                                     beach side, fine day in summer                                                sunshine, fine day in the afternoon                                (35,000)   sunshine, fine day at three o'clock                                10,000     sunshine, cloudy (32,000)                                                     sunshine, cloudy, one hour after sunrise                                      (2,000)                                                            1,000      window side at the office under                                               fluorescent                                                                   lamp (1,000)                                                                  sunshine, fine day, one hour after sunset                                     (1,000)                                                                       shopping space in department store (500-                                      700)                                                               500        ticket gate at station (650)                                                  office under fluorescent lamp (400-500)                                       eight mat space under two fluorescent                                         (30 W) lamp (300))                                                 300        subway platform (300)                                              100        arcade in the night (150-200)                                      10         movie theater, intermisson time (15-35)                                       candle light (10-15)                                               ______________________________________                                    

In the microcomputer 10, white balance is controlled as follows. Themicrocomputer 10 increases (decreases) the values of the white balancecontrol signals Rcont and Bcont step by step in order to make thedifference between the integral averaged value of the color differencesignals R-Y and B-Y and the reference values less than a value forjudging convergence (for example, 10LSB [Least Significant Bit]). Whenthe differences between the integral averaged values of the colordifference signals and the reference values are less than the values forjudging convergence for operating white balance control signals at themost suitable color temperature, the values of the white balance controlsignals Rcont and Bcont become constant.

In the outdoor mode, the values of the white balance control signals arepositioned within the region Y. In the indoor mode, the values of thewhite balance control signals are positioned within the region X. If thevalues of the white balance control signals Rcont and Bcont areconverged to constant values within the region X, white balance controlis properly operated.

In addition, when white balance is automatically controlled and anoccurrence of color failure is reduced regardless of natural light andartificial light in the outdoor and indoor modes, a controlled region ofthe white balance control signals Rcont and Bcont is widened as shown bya region X surrounded with a broken line in FIG. 15. To widen thecontrolled region, an occurrence of color failure is increased, sincethe other factors, except for the information of color temperature,effect the white balance control. The seventh embodiment of the presentinvention provides the outdoor mode and the indoor mode. In the outdoormode, white balance is controlled within a region corresponding to arespective value of color temperature under natural light. In the indoormode, white balance is controlled within a region corresponding to arespective value of color temperature under artifical light. Therefore,the region of the white balance control is restrictively limited. Evenif Green Grass and a red wall is photographed of which the averagedcolor of all colors in a picture is not an achromatic color, anoccurrence of color failure is remarkably reduced and white balance iscontrolled properly.

In the seventh embodiment of the present invnetion, after the values ofthe white balance control signals Rcont and Bcont are converged tovalues within the region Y, the values of the white balance controlsignals Rcont and Bcont are shifted to the region X in the indoor mode,only when the following two conditions are satisfied.

(1) The brightness values of the object are less than a value for theswitching modes.

(2) The difference between integral averaged values for color differencesignals R-Y and B-Y and the reference values is more than the widenedconverged value for judging (for example, 30LSB), where the widenedconverged value for judging (30LSB) is slightly greater than theconverged value for judging (10LSB).

When an object is photographed outdoors, even if the above condition (1)is satisfied by photographing a dark object, the values of the whitebalance control signals Rcont and Bcont are not shifted to the region Xin the indoor mode because the condition (2) is not satisfied. Thus,when a dark object is photographed outdoors, the white balance isproperly controlled by the values of the white balance control signalswithin the region Y for the outdoor mode so that the object isphotographed properly. If a region is changed by only having condition(1) satisfied, when a dark object is photographed outdoors, the valuesof the white balance control signals are shifted to the region X for theoutdoor mode, so that the white balance cannot be controlled properly.On the other hand, when a person who is photographing outdoors entersinto a house with a camera, the above conditions (1) and (2) aresatisfied, so that the values of the white balance control signals Rcontand Bcont are shifted to the region X for the indoor mode and whitebalance is properly controlled indoors.

In the seventh embodiment of the present invention, after the values ofthe white balance control signals Rcont and Bcont are converged at thevalues within the region X for the indoor mode, the values of the whitebalance control signals Rcont and Bcont are shifted to the values withinthe region Y for the outdoor mode, only when the following conditionsare satisfied.

(3) The brightness values of an object are greater than a value for theswitching modes

(4) The difference between integral averaged values for color differencesignals R-Y and B-Y and the reference values is more than the widenedconverged value for judging (for example, 30LSB) where the widenedconverged value for judging (30LSB) is slightly greater than theconverged value for judging (10LSB).

When an object is photographed indoors, even if the above condition (3)is satisfied by photographing with a light source such as an electricbulb, the values of the white balance control signals Rcont and Bcontare not shifted to the region Y in the indoor mode, since the condition(4) is not satisfied. Thus, when a light source such as an electric bulbis used for photographing indoors, the white balance is properlycontrolled by the values of the white balance control signals within theregion X for the indoor mode so that the object is photographedproperly. If a region is changed by only having condition (3) satisfied,when a light source such as an electric bulb is used for photographingindoors, the values of the white balance control signals are shifted tothe region Y for the indoor mode, so that the White balance cannot becontrolled properly. On the other hand, when a person who isphotographing indoors Goes outdoors with a camera, the above conditions(3) and (4) are satisfied, so that the values of the white balancecontrol signals Rcont and Bcont are shifted to the region Y for theindoor mode and white balance is properly controlled outdoors.

When the values are shifted from the region X to the region Y, thevalues change to values located in the region Y nearest to the region X.Similarly, when the values are shifted from the region Y to the regionX, the values change to converged values located in the region X nearestto the region Y.

In the present embodiment, the indoor and outdoor modes are changeddepending on a brightness value for switching, that is, a value forswitching modes may be selected for the most suitable value inaccordance with the type of video camera. The regions X and Y may beoptionally selected in accordance with a design of a video camera.

Next, a control operation of the seventh embodiment will be explainedaccording to the present invention with reference to FIG. 16. A batterysource is switched on in a step 401, a value of the white balancecontrol signal for a red signal as an initial value and a value of awhite balance control signal for a blue signal as an initial value areoutput from the microcomputer 10 so that the initial values are preset.Next, the microcomputer 10 inputs integral averaged values for colordifference signals R-Y and B-Y which are white balance controlleddepending on the values of the white balance control signals Rcont andBcont as the initial values in a step 403. In a step 404, it is judgedwhether a difference between the integral averaged values of the colordifference signals R-Y and B-Y and the reference values are more thanthe predetermined values (for example, 10LSB [Least Significant Bit]).If the judgement is YES, the values converge and the operation returnsto the step 403. If the judgement is NO, the values do not converge andthe operation goes to a step 405.

In the step 405, brightness values are detected by inputing brightnessdata. In a step 406, if the brightness value of an object is more than avalue for the switching mode, the region Y is selected for the outdoormode and if the brightness value of an object is less than a value forthe switching mode, the region X is selected for the indoor mode. In astep 407, it is judged whether a selected region is different from aprevious region. If the selected region is the same as the previousregion, the operation returns to a step 409.

In a step 408, a region is selected which is the same as the previousregion and a varying direction of the white balance control is computedin a step 409. If the values of the white balance control signals Rcontand Bcont are within the region (the decision is to be judged YES in astep 410), the white balance control signals Rcont and Bcont are outputof which the values are changed by one step value. If the values of thewhite balance control signals Rcont and Bcont are not within the region(the decision is judged to be NO in the step 410), renewed values of thewhite balance control signals Rcont and Bcont are not output.

If it is judged that the selected region is different from the previousregion in the step 407, it is judged whether the values converge once ina step 412. After the values converge once (the decision is judged to beYES in the step 412), when a difference between integral values of thecolor difference signals R-Y and B-Y and the reference values are morethan enlarged converged values, the operation goes to the step 408.Therein, the selected region is not utilized and the previous region isstill utilized. Such an operation is operated when a light source isphotographed indoors and a dark object is photographed outdoors.

When the decision is judged to be NO in a step 412 or the values of thewhite balance control signals Rcont and Bcont are converged once (thedecision is judged to be YES in the step 412) and a difference betweenintegral averaged values of color difference signals R-Y and B-Y and thereference values are more than enlarged converged values, the operationgoes to a step 414. In the step 414, a region is changed to the regionwhich is selected in the step 406, and the white balance control signalsof which the values are positioned in the selected region are output.Such an operation is operated when a person who is photographing indoorsgoes outdoors or a person who is photographing outdoors goes indoors.

Next, the eighth embodiment of the present invention will be describedwith an explanation of an operation of the microcomputer 10. As shown bya flow chart in FIG. 17, a kind of a light source is selected in step501 and then an initial operation for white balance control is actuatedin step 502. As shown in FIG. 4, an initial value r-0 as the whitebalance control signal Rcont for a red signal and an initial value b-0as the white balance control signal Bcont for a blue signal are outputfrom the microcomputer 10. In a step 503, a variable region B is set.Then, integral averaged values of color difference signals white balancecontrolled R-Y and B-Y, which correspond to the values and b-0 of thewhite balance control signals Rcont and Bcont, are input to themicrocomputer 10 and the integral averaged values of the colordifference signals R-Y and B-Y and the reference values are compared ina step 504. As a result of a comparison, if differences between theintegral averaged values of the color difference signals and thereference values are more than predetermined values, values of the whitebalance control signals Rcont and Bcont are stepped up (down) and thenoutput. The values of the white balance control signals Rcont and Bcontare successively stepped up (down) and output until the differencesbetween the integral averaged values of the color difference signals R-Yand B-Y and the reference values are less than the predetermined values.When the differences are less than the predetermined values (forexample, 10LSB [Least Significant Bit]), the values of the white balancecontrol signals Rcont and Bcont become constant. However, the values ofthe white balance control signals Rcont and Bcont are limited within thevariable region β in accordance with the kind of selected light source.

Further, the operation of steps 504 through 508 as shown in FIG. 17 willbe explained. As described above, integral averaged values of the colordifference signals R-Y and B-Y are input in the step 504 and then it isjudged whether the integral averaged values of the color differencesignals R-Y and B-Y and the reference values are less than thepredetermined values in a step 505. If the difference is more than thepredetermined values, then the white balance control is improper and theoperation returns to the step 504 and the integral averaged values ofthe color difference signals R-Y and B-Y are input.

In the step 507, it is judged whether the present values of the whitebalance control signals Rcont and Bcont are within the variable region βselected in the step 503. If the values are within the variable regionβ, the operation goes to a step 508. In the step 508, the white balancecontrol signals Rcont and Bcont are increased or decreased by one stepvalue. In the step 506, it is judged whether the values should beincreased or decreased. If the values are positioned out of the variableregion β, the white balance control signals Rcont and Bcont are notoutput and the operation returns to the step 504.

After repeating an operation of the steps 504, 505, 506, 507, and 508 ofa flow chart, the values of the white balance control signals Rcont andBcont are successively changed within the variable region β. Gains of ared signal circuit and a blue signal circuit are changed within avariable region so that a deterioration of the reproduced color does notoccur even though there is a difference between a selected light sourceand an actual color temperature.

As described above, according to the first embodiment of the presentinvention, a variable amount of white balance control signals arelimited in the variable region so that color failure is prevented fromoccurring even if an object is photographed in which one specific colordominates.

The variable region can be renewed by the values of the white balancecontrol signals converged or fixed. Thereby, a proper white balance iscontrolled even if the color temperature of the object is actuallychanged.

According to the second embodiment of the present invention, a variableregion becomes narrow in a telescope condition for zooming. Thereby,color failure is prevented from occurring in the telescope condition.

According to the third- and fourth- embodiments of the presentinvention, values of white balance control signals are changed in orderto equalize integral averaged values of color difference signals and thereference values when a difference between a present brightness valueand a brightness value at the last converged time is more than arecognition level for changing brightness. Thereby, the white balancecontrol device can control white balance properly without having colorfailure occur when an object is photographed under a light source orwithout a light source.

According to the fifth embodiment of the present invention, when adifference between the integral averaged values of color differencesignals and the reference values is more than the switching values, thatis, the values of the white balance control signals are quite differentfrom the converged values, a converging period becomes shorter sinceoutput intervals of the white balance control signals are made to beshorter. When the difference between the integral averaged values andthe reference values are less than the switching values, that is, thevalues of the white balance control signals are near to the convergedvalues, the values are accurately converged without the occurrence ofany hunting since output intervals of the white balance control signalsare made to be longer.

According to the sixth embodiment of the present invnetion, after thevalues are converged once, output intervals of white balance controlsignals are made to be longer. When a color of an object is suddenlychanged, white balance can be continuously controlled without changingthe control condition of the white balance.

According to the seventh embodiment of the present invention, an outdoormode and an indoor mode are provided and controllable regions are setfor each mode in order to control white balance in the best condition.

In the seventh embodiment, after the white balance control signalsconverge once, a change from the outdoor mode to the indoor mode occursresponsive not only to the brightness value of an object but also to adifference between integral averaged values of color difference signalsand the reference values. Therefore, a region for a corresponding modeis not changed even if a light object is photographed indoors and a darkobject is photographed outdoors so that white balance is properlycontrolled. The region for the corresponding mode is changed when acolor temperature is actually changed from an indoor condition to anoutdoor condition.

According to the eighth embodiment of the present invention, when alight source is manually selected, a variable region is changed inaccordance with a light source selected from white balance controlsignals, so that the white balance is properly controlled without adeterioration of the reproduced color even if there is a slightdifference between a selected light source and an actual colortemperature.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adepature from the sprit and scope of the invention, and all suchmodification as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

We claim:
 1. A white balance control device in a video recording devicehaving zoom capabilities comprising:white balance control means forcontrolling white balance by controlling an amplification degree of ared elementary color signal and a blue elementary color signal out ofred-, green-, and blue- elementary color signals; matrixing color meansfor outputting first and second color difference signals by processingelementary color signals white balance controlled by said white balancecontrol means; and processing means for setting a recognition level as afunction of zoom information, the recognition level being used forchanging a brightness value, and for actuating said white balancecontrol means in order to equalize integral averaged values of saidfirst and second color difference signals and reference values, andpredetermined integral averaged values for each of said first and secondcolor difference signal are set as said reference values when anaveraged color of all colors in a picture becomes an achromatic color ata reference color temperature.
 2. A white balance control device asclaimed in claim 1, wherein said processing means transmits whitebalance control signals to said white balance control means and thewhite balance control device further comprising:control means forinputting zoom information after a battery source is turned on and thevalue of said white balance control signals converge, wherein saidprocessing means increases said reference values when a zooming positionis in a telescope condition or a brightness value of an object is high,said processing means decreases said reference values when said zoomingposition is in a wide condition or said brightness value of an object isslow so that a recognition level for changing a brightness value can bedetermined and said values of said white balance control signals arechanged in order to equalize said integral averaged values of each saidfirst and second color difference signal and said respective referencevalues when a difference between a present brightness value and abrightness value at a last converged time is more than said recognitionlevel for changing the brightness value.
 3. A method for controllingwhite balance control signals in a video recording device having zoomcapabilities, comprising the steps of:(a) controlling white balance bycontrolling an amplification degree of a red elementary color signal anda blue elementary color signal out of red-, green-, and blue- elementarycolor signals; (b) outputting first and second color difference signalsby processing elementary color signals white balanced controlled by saidstep (a); (c) setting a recognition level as a function of zoominformation, the recognition level being used for changing a brightnessvalue; and (d) actuating said step (a) in order to equalize integralaveraged values of said first and second color difference signals andreference values, and predetermined integral average values for each ofsaid first and second color difference signals are set as said referencevalues when an averaged color of all colors in a picture becomes anachromatic color at a reference color temperature.
 4. A method forcontrolling white balance control signals as claimed in claim 3, whereinsaid step (d) transmits the white balance control signals to said step(a), and wherein the step (c) includes:(c) inputting zoom informationafter a battery source is turned on and the value of the white balancecontrol signals converge, wherein said step (d) increases said referencevalues when a zooming position is in a telescope condition or abrightness value of an object is high, said step (d) decreases saidreference values when said zooming position is in a wide condition orsaid brightness value of an object is low so that a recognition levelfor changing a brightness value can be determined and said values ofsaid white balance control signals are changed in order to equalize saidintegral averaged values of each said first and second color differencesignal and said respective reference values when a difference between apresent brightness value and a brightness value at a last converged timeis more than said recognition level for changing the brightness value.5. A white balance control device comprising:white balance control meansfor controlling white balance by controlling an amplification degree ofa red elementary color signal and a blue elementary color signal out ofred-, green-, and blue- elementary color signals; matrixing color meansfor outputting first and second color difference signals by processingelementary color signals white balance controlled by said white balancecontrol means; processing means for transmitting white balance controlsignals to said white balance control means, wherein said white balancecontrol means is actuated in order to equalize integral averaged valuesof said first and second color difference signals and reference values,and predetermined integral averaged values for each first and secondcolor difference signal are set as said reference values when anaveraged color of all colors in a picture becomes an achromatic color ata reference color temperature; and control means for inputting zoominformation after a battery source is turned on and values of whitebalance control signals converge, wherein said processing meansincreases said reference values when a zooming position is in atelescope condition or a brightness value of an object is high, saidprocessing means decreases said reference values when said zoomingposition is in a wide condition or said brightness value of an object islow so that a recognition level for changing a brightness value can bedetermined and said values of said white balance control signals arechanged in order to equalize said integral averaged values of each saidfirst and second color difference signal and said respective referencevalues when a difference between a present brightness value and abrightness value at a last converged time is more than said recognitionlevel for changing the brightness value.
 6. A method for controllingwhite balance control signals comprising the steps of:(a) controllingwhite balance by controlling an amplification degree of a red elementarycolor signal and a blue elementary color signal out of red-, green-, andblue- elementary color signals; (b) outputting first and second colordifference signals by processing elementary color signals white balancecontrolled by said step (a); (c) transmitting white balance controlsignals to said step (a), wherein said step (a) is actuated in order toequalize integral averaged values of said first and second colordifference signals and reference values, and predetermined integralaveraged values for each first and second color difference signal areset as said reference values when an averaged color of all colors in apicture becomes an achromatic color at a reference color temperature;and (d) inputting zoom information after a battery source is turned onand values of white balance control signals converge, wherein said step(c) increases said reference values when a zooming position is in atelescope condition or a brightness value of an object is high, saidstep (c) decreases said reference values when said zooming position isin a wide condition or said brightness value of an object is low so thata recognition level for changing a brightness value can be determinedand said values of said white balance control signals are changed inorder to equalize said integral averaged values of each said first andsecond color difference signal and said respective reference values whena difference between a present brightness value and a brightness valueat a last converged time is more than said recognition level forchanging the brightness value.
 7. A white balance control device in avideo recording device having zoom capabilities comprising:white balancecontrol means for controlling white balance by controlling anamplification degree of a red elementary color signal and a blueelementary color signal out of red-, green-, and blue- elementary colorsignals; matrixing color means for outputting first and second colordifference signals by processing elementary color signals white balancecontrolled by said white balance control means; and processing means forsetting a recognition level as a function of zoom information and foractuating said white balance control means in order to equalize integralaveraged values of said first and second color difference signals andreference values, and predetermined integral averaged values for each ofsaid first and second color difference signal are set as said referencevalues when an averaged color of all colors in a picture becomes anachromatic color at a reference color temperature; wherein saidprocessing means transmits white balance control signals to said whitebalance control means; the white balance control device furthercomprising: control means for inputting zoom information after a batterysource is turned on and the value of said white balance control signalsconverge, wherein said processing means increases said reference valueswhen a zooming position is in a telescope condition or a brightnessvalue of an object is high, said processing means decreases saidreference values when said zooming position is in a wide condition orsaid brightness value of an object is slow so that a recognition levelfor changing a brightness value can be determined and said values ofsaid white balance control signals are changed in order to equalize saidintegral averaged values of each said first and second color differencesignal and said respective reference values when a difference between apresent brightness value and a brightness value at a last converged timeis more than said recognition level for changing the brightness value.8. A method for controlling white balance control signals in a videorecording device having zoom capabilities, comprising the steps of:(a)controlling white balance by controlling an amplification degree of ared elementary color signal and a blue elementary color signal out ofred-, green-, and blue- elementary color signals; (b) outputting firstand second color difference signals by processing elementary colorsignals white balanced controlled by said step (a); (c) setting arecognition level as a function of zoom information; and (d) actuatingsaid step (a) in order to equalize integral averaged values of saidfirst and second color difference signals and reference values, andpredetermined integral average values for each of said first and secondcolor difference signals are set as said reference values when anaveraged color of all colors in a picture becomes an achromatic color ata reference color temperature; wherein said step (d) transmits the whitebalance control signals to said step (a); wherein the step (c) includes:(c₁) inputting zoom information after a battery source is turned on andthe value of the white balance control signals converge, wherein saidstep (d) increases said reference values when a zooming position is in atelescope condition or a brightness value of an object is high, saidstep (d) decreases said reference values when said zooming position isin a wide condition or said brightness value of an object is low so thata recognition level for changing a brightness value can be determinedand said values of said white balance control signals are changed inorder to equalize said integral averaged values of each said first andsecond color difference signal and said respective reference values whena difference between a present brightness value and a brightness valueat a last converged time is more than said recognition level forchanging the brightness value.